\Wil"low-herb`\, n. (Bot.)
A perennial herb ({Epilobium spicatum}) with narrow
willowlike leaves and showy rose-purple flowers. The name is
sometimes made to include other species of the same genus.

{Spiked willow-herb}, a perennial herb ({Lythrum Salicaria})
   with willowy leaves and spiked purplish flowers.